Shallow subtidal octocorals in an Irish marine reserve

Abstract

Alcyonacean octocorals are anthozoans which are found in many coastal benthic habitats, where they can be sensitive to environmental and/or anthropogenic stress. As part of a two-decade monitoring study of Lough Hyne (Europe’s first marine reserve and Ireland’s only one), we documented benthic communities at rocky-shore sites. As a fully marine, semi-enclosed, tidal ‘lake’ connected to the Atlantic Ocean via tidal rapids, Lough Hyne has long been noted for its high species and habitat diversity. One of the noteworthy guilds we report here was the alcyonacean octocorals: (1) the soft coral Alcyonium hibernicum under shallow subtidal rocks at monitoring sites in the lough from 2002 to 2015 and (2) the first known records (2013 to present) of the red soft coral A. glomeratum inside the lough (above the rapids). Furthermore, in August/September 2014 and 2015, we rediscovered the stoloniferous octocoral Sarcodictyon catenatum, last reported in the lough in the 1930s. We documented the distribution and abundance of these species in shallow subtidal areas of the lough as a baseline in the face of rapidly degrading conditions due to extreme oxygen fluctuations from eutrophication.